1. Field of the Art
This invention relates to a screen retractor mechanism for an accordion type net screen or the like which is foldably stretchable to cover an opening in a housing structure, for example, for blinding or shading purposes or for blocking intrusion of insects through the opening.
2. Description of the Prior Art
For the purpose of shielding off insects or shading or blinding an opening in a housing wall, there have thus far been known in the art the screen transport mechanisms which are designed to open and close, horizontally toward and away from one side of the opening, an accordion type screen with a large number of pleats which are foldably unfoldable to stretch the screen. The accordion type screen of this sort has an advantage that it can be accommodated in a far smaller space as compared with a roll type screen which is designed to be wound on a take-up roll.
In the existing screen transport mechanism as mentioned above, the accordion screen, which is foldable along a large number of pleats in the fashion of the accordion, is fixed at its base end to a receptacle box frame which constitutes one of side frame members of a screen support frame structure, and a movable frame attached to the fore end of the screen and slidable along the screen support frame for opening and closing the screen. Due to the existence of pleats, the screen of this sort is almost in a free state, so that, even in a stretched state, it is easily put in flapping or wavering motions under the influence of winds or other external forces. In order to prevent such flapping movements and to stabilize the posture of the screen, it becomes necessary to thread a suitable number of tension cords through the screen and to maintain the tension cords constantly in a predetermined degree of tautness between the movable frame and receptacle frame.
In the case of an accordion screen, which is arranged to be closed or opened through operation of the above-mentioned movable frame, for preventing the flapping movements of the screen in the winds and to facilitate the operation of the movable frame, it is advantageous from the standpoint of cost to provide a pendant weight which is connected to base ends of the tension cords and suspended vertically movably within the receptacle box frame to maintain the tension cords in a taut state.
It is also conceivable to employ a spring as a means for keeping the tautness of the tension cords, which however is very likely to undergo deteriorations in tensile force when used repeatedly over a long period of time and needs to be of an extremely large length to make the tensile strength uniform under all conditions including the stretched state as well as the folded state of the screen, despite a substantial increase in cost.
In the above-described retractor construction using a pendant weight on the tension cords, as soon as a latch member on the movable frame is released from a latch lock member on an opposite side frame, the movable frame is automatically driven in the screen opening direction to retract the screen into the receptacle frame by the action of the pendant weight which is connected to the base ends of the respective tension cords. When the screen is in the stretched or closed state, the tautness of the tension cords is maintained by the pendant weight to ensure that the screen retain its posture in a stabilized state almost free of flapping motions which would otherwise be caused in a marked degree under the influence of winds or the like.
In case a pendant weight is used for suppressing to a minimum the waving motions of the screen as caused by winds or the like, it is necessary for the pendant weight to be heavy enough for applying high tension to the tension cords. However, if the pendant weight is too heavy, it is very likely for the movable frame to collide violently against the receptacle box frame when the latch member is released to open the screen automatically. The collision makes surprisingly large noises, and the impacts of the collision might cause serious damages to the retractor.
Therefore, while considering the use of a pendant weight of a relatively large weight, it is necessary to provide measures which will prevent the movable frame from hitting violently against the receptacle box frame at the time of opening the screen.